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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



conditions as nearly as possible alike do not necessarily 

 give similar results. This applies with particular force 

 to hauls made with small apparatus and for a short time. 

 As might be expected, hauls made on the same area with 

 large nets and extending over a considerable distance give 

 results which are much more similar than in the eases 

 given above. Three hauls witnessed by Dr. Pulton* 

 illustrate this. They were made by a commercial trawler 

 working in the Moray Firth on September 3rd, 1900, and 

 using an otter trawl with a head line measuring 120 feet. 

 The results were, for the more important fishes : 





I. 

 1-45 a.m. 



to 

 6-45 a.m. 



II. 

 7-40 a.m. 



to 

 12-40 p.m. 



III. 

 1-20 p.m. 



to 

 6-30 p.m. 



Cod 



49 

 ]640 

 92 

 119 

 68 

 12 



34 

 2407 

 52 

 92 

 35 

 8 



71 



Haddock 



2202 



Whiting 



291 



Witches .. 



7 



Long rough Dabs... 

 Sail-Flukes 



49 

 3 







Here the catches are more similar, though in the case of 

 some of the fishes there is a considerable difference 

 between the numbers caught. But it is obvious that a 

 longer haul and with a larger net, must, by merely 

 covering a greater area, tend to eliminate lesser 

 inequalities of distribution. 



(2) The Effect of The State of Tide. 



This is difficult to study since a suitable experiment 

 would necessitate trawling over the same line at least 

 half-a-dozen times a day for a fortnight, and during that- 

 time considerable changes in the density of the fish might 

 occur. But such an experiment repeated several times 



* 19th Rep. Scottish Fish. Board, 1901, p. 67. 



